1. Field of the Invention
The present invention relates to a process for a trench capacitor in a semiconductor device, more specifically, to a method for forming a bottle shaped deep trench for a deep trench capacitor.
2. Description of the Prior Art
As the semiconductor memory such as DRAM is getting more and more compact, to avoid occupying large area but maintain high capacitance, the techniques for trench capacitors are widely developed.
In order to increase capacitance, one of the methods is to increase the critical dimension of a deep trench for forming the trench capacitor in the semiconductor device. However, if the opening of the deep trench is too large, the area of the active area is occupied. Accordingly, a technique for a “bottle shaped” trench structure is developed.
The present invention provides a novel method for forming a bottle shaped deep trench for making a trench capacitor. By the method in accordance with the present invention, the bottle shaped deep trench can be formed through simple processing steps.